This invention relates to safety closure caps adapted for sealing containers having orifices defined by an annular rim. More particularly this invention relates to safety closure caps which vent gasses when the pressure in the container exceeds a given value, and which seal the container when the internal pressure in the container is below a given value, thereby preventing moisture in the atmosphere from contacting the contents of the container.
Many products formulated for use as household products such as drain cleaners, toilet bowl cleaners, and the like are sold in containers or vessels having at least one opening through which the product is dispensed. To be effective many of these products are potent and, therefore, may be harmful if ingested by a child. Thus, it is necessary that a container closure intended for use with such household product be constructed so that is would be quite difficult, if not impossible, for a child to remove and yet easily removed by the intended year. Further, since these products, as sold, contain sufficient amounts of the product to enable multiple uses, the closure cap must also be relatively easy for the intended user to replace on the container.
In addition to the considerations discussed above, the closure cap must also be relatively inexpensive. Since the product is relatively inexpensive, it would not be economically feasible to use a closure that substantially adds to the cost of the end product.
Another problem which is encountered with these household products is in storing them in warehouses prior to sale. When temperatures in the warehouse are not controlled so that they become elevated the product stored in the individual containers may tend to react to form gasses. This will create excessive pressure in the container, and may cause the caps to pop off the containers. Therefore, it is desirable that closure caps used with these products have a mechanism for venting these gasses. However, since most of these products would tend to become less effective or deactivate if exposed to the moisture in the atmosphere it is also necessary that the closure be able to seal the contents of the container from contact with the atmosphere both before and after venting.
A further problem encountered in storing these types of products in a warehouse is created by the necessity of stacking the containers one on top of another. In stacking, if the weight from an upper container is allowed to rest on the closure cap of a lower container, the cap could be deformed thereby possible causing it to become defective. Therefore, it is necessary that the weight of an upper container be supported by the lower container rather than the cap, thereby preventing the total weight from resting directly on the closure.
Safety closure caps known in the prior art are exemplified by U.S. Pat. No. 4,043,473 to McCord and U.S. Pat. No. 3,966,082 to Hopkins.
The McCord patent discloses a plug-type closure which has several lugs disposed on the bottom of the plug which cooperate with recesses formed in the orifice of the container to lock the closure into the container thereby rendering it difficult for a child to open.
The Hopkins patent discloses a two part safety closure comprised of a rotatable annular collar and a snap fit overcap. The overcap is locked onto the container through the annular collar.
A drawback of these prior art safety caps is that they don't provide a mechanism for releasing excessive pressure within a container.